The invention relates to a joint making it possible to connect two ultra-high frequency waveguides, having a rectangular section and a common longitudinal axis, and which are able to have a relative rotary movement about their commong longitudinal axis.
It is more particularly usable in the case of a connection of a pivoting antenna equipping a satellite. Such an antenna has two positions, namely a first position in which it is bent back against the satellite in order that it can be held in the volume defined by the cover protecting the satellite during its launch, and a second or operating position, when it is opened out after the satellite has reached orbit. The rotation angle is then below 360.degree. and the second position is fixed.
The antenna is connected by two waveguide sections to transmission or reception equipment on board the satellite. One section is integral with the antenna and the other section is integral with the satellite. The junction between the fixed section and the moving section must be brought about by a device which does not attenuate the signal and which is reliable in a temperature range from -150.degree. to +200.degree. C., in the presence of radiation.
It is known to use a flexible waveguide, but the greater the rotation angle, the longer said guide. Its losses are by no means negligible and vary in a random manner as a function of the conformation taken by the guide after the opening out of the antenna. It is also known to bring about a connection by a flexible coaxial cable, but this leads to by no means negligible losses and its insulation finds it difficult to withstand extreme temperatures. These two devices require a relatively powerful motor and a certain energy consumption for opening out the antenna.
It is also known to construct joints, which rotate by more than 360.degree., by the contactless connection of two coaxial lines, whereby their outer conductors on the one hand and their inner conductors on the other face one another over a length equal to quarter the wavelength. This device has a complicated and costly construction when losses must be minimized.
Finally it is known to bring about a change in the propagation mode of the waves for passing them from a guide having a rectangular section to a guide with a circular section by providing a rotary joint on said circular guide and then again changing the mode in order to again pass the waves into a rectangular guide. The disadvantage of this device is that is requires two mode changes, so that the resulting losses are not neglibible.